Hello All,I recently wanted to fit a VHF radio to my car, however the car I have is a small city car with a tiny battery. I did not want to risk killing the car battery should I be sitting portable for any length of time. So I had the idea to use an old car battery and put a solar panel connected to charge controller & fuse box mounted in the boot to run the radios from. I made a video of it if anyone wants to see the link is here.I am planning to be able to add things to this as and when I need them, I might be sitting camped up for a while and I would like to be able to run lights and other radio equipment from it, hence the fuse box and the solar controller to protect the battery.To this end the solar controller is a 20Amp & I am using wire rated for 20 amps running from the battery and from the solar controller to the fuse box. The radio I have plugged in only pulls a max of around 2.1Amp when transmitting so I have plenty of room for additional devices.I have also upgraded the solar panel (the first picture is the new one) the small one mounted in the side window was only about 0.5watts. I worked out for the old car battery I am using in order to charge it properly I need a 17watt panelthe equation to work it out is pretty simple(Battery Amp Hour)x (battery voltage) = (Watt hour)You then work out how many hours of charging you will have, so if you want it to charge daily I worked out I have 6 hours of good day light to charge with so you then devide the watt hourage by the charging time(watt hour) / (charging time)So for my set up the numbers look like this44Ahr x 12v = 528Whr528Whr / 6 = 88Watts (this is to charge daily from compleastly flat battery528Whr / 30 = 17.6Watts (this is what I used, this is to charge the battery weekly)Also a point to note is in order to get the best out of your battery, you should not discharge it at a rate higher than its Amp hour / 10 i.e my 44Ahr battery should not be discharged at a constant current higher than 4.4Amps. It will still work doing this and it is fine for short stints but prolonged excessive draw will make the battery less efficient.Now I know what you are thinking, a car lead acid battery has so many downsides, Hydrogen as a byproduct, can only really supply 50% of its rated amp hours & it's not suited to being drained and charged in such a way. Well I have one thing to say to that...... You are right, it is the next thing on my list to replace.Also its not in the pictures but the Battery has been bolted down to stop it moving around and n the event of a car crash it shouldn't become a projectile.https://ift.tt/2WtaVUE via /r/DIY https://ift.tt/2HJwYD9
